We had an advisor with my middle son and I felt like it hurt us after talking to some pro scouts later. He was giving out mixed information that did not come from us. I felt like it cost my son a chance at a good draft pick because he was throwing out numbers that were unrealistic for where my son was. He also was telling scouts it was on the mound or nothing and son would gladly have taken 1st and hit at the time. I was frustrated and bewildered how a guy could come up with the stuff he had told guys without consulting us.
On last son, we were asked a few times by advisors and declined. There was one who kept coming around and never really offered his services but kept telling us that he felt like son's best option was to go to college with the offer he had and the skillset he had. We talked to several scouts and upper guys and the money was never where we felt it needed to be so I'm sure they passed due to those conversations.
I think you can find out quickly when you ask for references and their list of clients. That will tell you a lot about who they are and what kind of person they represent. The real deals will gladly provide you with client lists and ask what they provided as agents for those guys. Ask about connections with not only the clubs but shoe companies, bat companies, and such. The great guys provide incredible resources outside just the negotiations with extras for their players.
As has been said. find the guys on here that have sons who have gone through it and PM them.